tunelp(8) Linux Programmer's Manual tunelp(8)
tunelp - set various parameters for the lp device
tunelp <device> [-i <IRQ> | -t <TIME> | -c <CHARS> | -w <WAIT> | -a [on|off] | -o [on|off]
| -C [on|off] | -r | -s | -q [on|off] | - T [on|off] ]
tunelp sets several parameters for the /dev/lp? devices, for better performance (or for
any performance at all, if your printer won't work without it...) Without parameters, it
tells whether the device is using interrupts, and if so, which one. With parameters, it
sets the device characteristics accordingly. The parameters are as follows:
specifies the IRQ to use for the parallel port in question. If this is set to
something non-zero, -t and -c have no effect. If your port does not use inter-
rupts, this option will make printing stop. The command tunelp -i 0 restores non-
interrupt driven (polling) action, and your printer should work again. If your
parallel port does support interrupts, interrupt-driven printing should be somewhat
faster and efficient, and will probably be desirable.
NOTE: This option will have no effect with kernel 2.1.131 or later since the irq is
handled by the parport driver. You can change the parport irq for example via
/proc/parport/*/irq. Read /usr/src/linux/Documentation/parport.txt for more
details on parport.
is the amount of time in jiffies that the driver waits if the printer doesn't take
a character for the number of tries dictated by the -c parameter. 10 is the
default value. If you want fastest possible printing, and don't care about system
load, you may set this to 0. If you don't care how fast your printer goes, or are
printing text on a slow printer with a buffer, then 500 (5 seconds) should be fine,
and will give you very low system load. This value generally should be lower for
printing graphics than text, by a factor of approximately 10, for best performance.
is the number of times to try to output a character to the printer before sleeping
for -t <TIME>. It is the number of times around a loop that tries to send a char-
acter to the printer. 120 appears to be a good value for most printers in polling
mode. 1000 is the default, because there are some printers that become jerky oth-
erwise, but you must set this to `1' to handle the maximal CPU efficiency if you
are using interrupts. If you have a very fast printer, a value of 10 might make
more sense even if in polling mode. If you have a really old printer, you can
increase this further.
Setting -t <TIME> to 0 is equivalent to setting -c <CHARS> to infinity.
is the number of usec we wait while playing with the strobe signal. While most
printers appear to be able to deal with an extremely short strobe, some printers
demand a longer one. Increasing this from the default 1 may make it possible to
print with those printers. This may also make it possible to use longer cables.
It's also possible to decrease this value to 0 if your printer is fast enough or
your machine is slow enough.
This is whether to abort on printer error - the default is not to. If you are sit-
ting at your computer, you probably want to be able to see an error and fix it, and
have the printer go on printing. On the other hand, if you aren't, you might
rather that your printer spooler find out that the printer isn't ready, quit try-
ing, and send you mail about it. The choice is yours.
This option is much like -a. It makes any open() of this device check to see that
the device is on-line and not reporting any out of paper or other errors. This is
the correct setting for most versions of lpd.
This option adds extra ("careful") error checking. When this option is on, the
printer driver will ensure that the printer is on-line and not reporting any out of
paper or other errors before sending data. This is particularly useful for print-
ers that normally appear to accept data when turned off.
NOTE: This option is obsolete because it's the default in 2.1.131 kernel or later.
-s This option returns the current printer status, both as a decimal number from
0..255, and as a list of active flags. When this option is specified, -q off,
turning off the display of the current IRQ, is implied.
This option tell the lp driver to trust or not the IRQ. This option makes sense
only if you are using interrupts. If you tell the lp driver to trust the irq,
then, when the lp driver will get an irq, it will send the next pending character
to the printer unconditionally, even if the printer still claims to be BUSY. This
is the only way to sleep on interrupt (and so the handle the irq printing effi-
ciently) at least on Epson Stylus Color Printers. The lp driver automagically
detects if you could get improved performance by setting this flag, and in such
case it will warn you with a kernel message.
NOTE: Trusting the irq is reported to corrupt the printing on some hardware, you
must try to know if your printer will work or not...
-r This option resets the port. It requires a Linux kernel version of 1.1.80 or
This option sets printing the display of the current IRQ setting.
-o, -C, and -s all require a Linux kernel version of 1.1.76 or later.
-C requires a Linux version prior to 2.1.131.
-T requires a Linux version of 2.1.131 or later.
By some unfortunate coincidence the ioctl LPSTRICT of 2.0.36 has the same number as the
ioctl LPTRUSTIRQ introduced in 2.1.131. So, use of the -T option on a 2.0.36 kernel with
an tunelp compiled under 2.1.131 or later may have unexpected effects.
tunelp 7 May 1999 tunelp(8)